U.S. patent application number 15/156632 was filed with the patent office on 2016-12-01 for lignite drying integration with a water/steam power cycle.
The applicant listed for this patent is ALSTOM Technology Ltd. Invention is credited to Thomas EDEL, Frederic GEIGER, Thierry POURCHOT, Didier WANTZ.
Application Number | 20160348540 15/156632 |
Document ID | / |
Family ID | 53397996 |
Filed Date | 2016-12-01 |
United States Patent
Application |
20160348540 |
Kind Code |
A1 |
EDEL; Thomas ; et
al. |
December 1, 2016 |
LIGNITE DRYING INTEGRATION WITH A WATER/STEAM POWER CYCLE
Abstract
The invention relates to power plant with a steam water power
cycle and a lignite dryer that uses steam from the steam water
power cycle. The connection of the lignite dryer to the steam water
power cycle includes a first extraction line and a second
extraction line.
Inventors: |
EDEL; Thomas; (Colmar,
FR) ; GEIGER; Frederic; (Giromagny, FR) ;
POURCHOT; Thierry; (Cravanche, FR) ; WANTZ;
Didier; (Bavilliers, FR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ALSTOM Technology Ltd |
Baden |
|
CH |
|
|
Family ID: |
53397996 |
Appl. No.: |
15/156632 |
Filed: |
May 17, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F01K 17/06 20130101;
F01K 7/22 20130101; F01K 7/38 20130101; F01K 7/16 20130101; F01K
7/44 20130101; F01K 7/40 20130101 |
International
Class: |
F01K 7/44 20060101
F01K007/44; F01K 7/22 20060101 F01K007/22 |
Foreign Application Data
Date |
Code |
Application Number |
May 26, 2015 |
EP |
15290140.1 |
Claims
1. A power plant comprising: a water/steam power cycle comprising:
a pressure series of steam turbines including: a high pressure
steam turbine; an intermediate pressure steam turbine; a low
pressure steam turbine; a re-heater fluidly located between the
high pressure steam turbine and the intermediate pressure steam
turbine; and a lignite dryer having: a heater connected to a steam
portion of the steam/water power cycle so as enable utilisation of
steam energy in the lignite dryer, wherein the connection to the
steam portion of the steam water power cycle comprises: a first
extraction line, fluidly connected to the water/steam power cycle
between the high pressure turbine and the intermediate pressure
steam turbine, the first extraction line further including an
ejector; a second extraction line, fluidly connected to the
water/steam power cycle between the intermediate pressure steam
turbine and the low pressure steam turbine, wherein the
configuration and location of the ejector and the connection of the
second extraction line to the ejector enables a lower pressure
steam in the second extraction line to be fed into the heater
together with a higher pressure steam of the first extraction
line.
2. The power plant of claim 1 wherein the second extraction line
includes a bypass fluidly connecting the first extraction line to
the second extraction line so as to bypass the ejector.
3. The power plant of claim 1 further comprises a de-superheater in
the first extraction line upstream of the ejector.
4. The power plant according to claim 1 further comprising a
throttle valve fluidly between the connection of the second
extraction line to the water/steam power cycle and the low pressure
steam turbine.
5. The power plant of claim 1, wherein the first extraction line is
connected to the water/steam power cycle between the re-heater and
the intermediate pressure steam turbine.
6. A method of controlling a power plant, comprising the steps of:
providing a water/steam power cycle comprising: a pressure series
of steam turbines including: a high pressure steam turbine; an
intermediate pressure steam turbine; and a low pressure steam
turbine; a re-heater fluidly between the high pressure steam
turbine and the intermediate pressure steam turbine; a throttle
valve fluidly between the intermediate pressure steam turbine and
the low pressure steam turbine; and providing a lignite dryer
having: a heater fluidly connected to a steam portion of the
steam/water power cycle so as to utilise steam energy in the
lignite dryer, wherein the connection to the steam portion of the
steam water power cycle comprises: a first extraction line,
connected to the water/steam power cycle between the high pressure
turbine and the intermediate pressure steam turbine to the heater,
including an ejector; and a second extraction line, fluidly
connected to the water/steam power cycle between the intermediate
pressure steam turbine and the throttle valve, and to the ejector,
the second extraction line further including a bypass, with a
bypass valve, to enable bypassing of the ejector; and controlling a
flow-rate to the heater by adjusting a pressure in the second
extraction line in conjunction with the bypass valve.
7. The method of claim 6 including the further steps of: providing
a first control valve in the first extraction line upstream of the
ejector; providing a second control valve in the second extraction
line upstream of the ejector; and controlling the flow-rate to the
heater in further conjunction with the first control valve and the
second control valve.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to European Patent
Application No. 15290140.1 filed May 26, 2015, the contents of
which are hereby incorporated in its entirety.
TECHNICAL FIELD
[0002] The present disclosure relates to integrate lignite drying
processes to improve both efficiency and cost-of-power generation
of a dry-lignite coal power plant applicable with or without CO2
capture. The disclosure further relates to arrangements for using
direct steam extraction from water/steam power cycle as an energy
source for lignite coal drying.
BACKGROUND INFORMATION
[0003] General principle of Lignite Drying in a lignite fired plant
is well known, using either hot flue gas extraction or steam
extraction from Water & Steam cycle or both to supply the
lignite drying system that includes beater mills, rotary drum
dryers and/or fluidized bed dryer.
[0004] Lignite drying techniques have been developed and tested in
order to use medium or low enthalpy heat to achieve partial or high
level of lignite pre-drying before pulverization, and gain
typically up to 3% point efficiency gains without heat recovery of
evaporation vapour of lignite moisture or 5% point efficiency gains
with heat recovery of evaporation vapour of lignite moisture. The
heat is either originating from low pressure steam extraction, or
from exhaust flue gas. These techniques sometime additionally use
mechanical or chemical dewatering processes.
[0005] U.S. Pat. No. 8,661,821 B2 in which superheated steam, which
has done partial work in a steam turbine, is extracted from a
water/stem power cycle and used as a drying medium to evaporate
moisture from coal powder. Condensate from the drying is then fed
into a deaerator of the steam turbine via a condensate pump for
recirculation. As discussed, the drying steam can be extracted from
any number of steam extraction points contained in the water/steam
power cycle.
SUMMARY
[0006] A power plant is disclosed that is intended to provide an
alternative means of thermally integrating a lignite dryer into a
water/steam cycle of the power plant using steam extraction.
[0007] It attempts to address this problem by means of the subject
matters of the independent claims. Advantageous embodiments are
given in the dependent claim.
[0008] An aspect includes power plant with a water/steam power
cycle, lignite dryer. The water/steam cycle comprises a pressure
series of steam turbines including a high pressure steam turbine,
an intermediate pressure steam turbine, and a low pressure steam
turbine. The cycle further includes a re-heater that is fluidly
located between the high pressure steam turbine and the
intermediate pressure steam turbine.
[0009] The lignite dryer includes a heater connected to a steam
portion of the steam/water power cycle so as to enable utilisation
of steam energy in the lignite dryer (10).
[0010] The connection to the steam portion of the steam water power
cycle comprises a first extraction line that is fluidly connected
to the water/steam power cycle between the re-heater and the
intermediate pressure steam turbine, or alternatively between the
high pressure turbine and the re-heater and to the heater. The
first extraction line further includes an ejector. The connection
further includes a second extraction line that is fluidly connected
to the water/steam power cycle between the intermediate pressure
steam turbine (34) and the low pressure steam turbine (35).
[0011] The configuration and location of the ejector and the
connection of the second extraction line to the ejector enables a
lower pressure steam in the second extraction line to be fed into
the heater together with a higher pressure steam in the first
extraction line.
[0012] In an aspect the second extraction line includes a bypass
that fluidly connects the first extraction line to the second
extraction line so as to bypass the ejector.
[0013] In further aspect the power plant includes a de-superheater
in the first extraction line upstream of the ejector.
[0014] In further aspect the power plant includes a throttle valve
fluidly located between the connection of the second extraction
line to the water/steam power cycle and the low pressure steam
turbine.
[0015] Another aspect includes a method of controlling a power
plant with lignite dryer. The method includes the steps of
providing a water/steam power cycle having a pressure series of
steam turbines including a high pressure steam turbine, an
intermediate pressure steam turbine, and a low pressure steam
turbine. The water/steam power cycle further includes a re-heater
fluidly between the high pressure steam turbine and the
intermediate pressure steam turbine and a throttle valve fluidly
between the intermediate pressure steam turbine and the low
pressure steam turbine.
[0016] The method further includes providing a lignite dryer having
a heater fluidly connected to a steam portion of the steam/water
power cycle so as to utilise steam energy in the lignite dryer,
wherein the connection to the steam portion of the steam water
power cycle comprises a first extraction line, connected to the
water/steam power cycle between the re-heater and the intermediate
pressure steam turbine or alternatively between the high pressure
turbine and the re-heater, to the heater, including an ejector and
further comprises a second extraction line that is fluidly
connected to the water/steam power cycle between the intermediate
pressure steam turbine and the throttle valve, the second
extraction line including a bypass, with a bypass valve.
[0017] The method includes the further step of controlling a
flow-rate to the heater by adjusting a pressure in the second
extraction line in conjunction with the bypass valve.
[0018] In a further aspect the method includes providing a first
control valve in the first extraction line upstream of the ejector
and a second control valve in the second extraction line upstream
of the ejector and then controlling the flow-rate to the heater in
further conjunction with the first control valve and the second
control valve.
[0019] Other aspects and advantages of the present disclosure will
become apparent from the following description, taken in connection
with the accompanying drawings which by way of example illustrate
exemplary embodiments.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] By way of example, an embodiment of the present disclosure
is described more fully hereinafter with reference to the
accompanying drawings, in which:
[0021] FIG. 1 is a schematic of a lignite fired power plant
according to an exemplary embodiment of the disclosure.
DETAILED DESCRIPTION
[0022] Exemplary embodiments of the present disclosure are now
described with references to the drawings, wherein like reference
numerals are used to refer to like elements throughout. In the
following description, for purposes of explanation, numerous
specific details are set forth to provide a thorough understanding
of the disclosure. However, the present disclosure may be practiced
without these specific details, and is not limited to the exemplary
embodiment disclosed herein.
[0023] FIG. 1 shows an exemplary embodiment of a power plant with a
drying system to dry pulverised lignite.
[0024] The drying includes an inlet line 11 for directing lignite
in the lignite dryer 10, a vapour outlet line 16 for exhausting
moisture laden gas from the lignite dryer and a solids outlet line
12 for discharging dried lignite for use in a combustor. The
lignite dryer 10 can be a Steam Fluidized Bed Dryer or a Steam
Heated Rotary Tube Dryer.
[0025] In an exemplary embodiment shown in FIG. 1, the power plant
includes a water/steam cycle a water/steam power cycle having a
pressure series of steam turbines 32,34,35, a condenser 38 at a low
pressure end of pressure series of steam turbines 32, 34,35
configured and arrange to condense steam exhausted from the low
pressure end of the pressure series of steam turbines, a low
pressure condensate system 40 arrangement downstream of the
condenser 38, adapted to preheat condensate from the condenser 38,
a high pressure condensate system 44 separated from the low
pressure condensate system 40 by a feed water tank 66, and boiler
50 for boiling and superheating condensate from the high pressure
condensate system 44 and to further and optionally performs the
function of a re-heater 52 for reheating steam between the pressure
series steam turbines 32,34,35.
[0026] In an exemplary embodiment shown in FIG. 1, a first
extraction line 104 extends from a point in the water/steam power
cycle between the re-heater 52 and the intermediate pressure steam
turbine to the heater 13 of the lignite dryer 10. This enables
extraction steam to be used as an energy source for the lignite
dryer 10. In an exemplary embodiment the first extraction line 104
includes a de-superheater.
[0027] In an exemplary embodiment, shown in FIG. 1, includes an
additional extraction line 101 with an ejector 106. This additional
extraction line 101 extends from a point of the water/steam cycle
located between the intermediate pressure steam turbine 34 and the
low pressure steam turbine 35 to the first extraction line 104 at
the ejector 106.
[0028] The ejector 106 is a device that operates using the venturi
principle. The device utilises higher pressure steam from the first
extraction line 104 to generate a high-velocity jet at the throat
of a convergent-divergent nozzle thus creating a low pressure at
that point. The low pressure point, which is the point at which
additional extraction line 101 connects to the first extraction
line 104, draws extraction steam from the lower pressure additional
extraction line. In this way lower pressure steam in the second
extraction line can be fed into the heater together with higher
pressure steam of the first extraction line 104.
[0029] In an exemplary embodiment shown in FIG. 1 the first
extraction line 104 includes a de-superheater 104b. In an exemplary
embodiment where the first extraction line 104 includes an ejector
106, the de-superheater 104b is located upstream of the ejector
106.
[0030] In an exemplary embodiment shown in FIG. 1 in which the
first extraction line 104 includes an ejector 106, the additional
extraction line 101 includes a bypass 103 with a bypass valve 101a,
connecting the first extraction line 104 to the second extraction
line 101 so as to bypass the ejector 106. This arrangement can be
used when the steam plant is operating a high or maximum load such
that the steam pressure in the additional extraction line 101 has
sufficient pressure and energy to supply the lignite dryer 10 while
maximising energy recovery in the intermediate pressure steam
turbine 34 by minimising extractions from this turbine.
[0031] In further exemplary embodiments shown in FIG. 1, a throttle
valve 102 is located in the water/steam power cycle between the
connection of the second extraction line 101 and the low pressure
steam turbine so as to enable control extraction pressure in the
additional extraction line 101. This can be achieved by coordinated
operation of the throttle valve 102 with the bypass valve 101a. For
example at full and very high loads throttle valve 102 is fully
opened while the bypass valve 101a is used to control supply
pressure at adequate level. As load decreases, resulting in a lower
low pressure steam turbine 35 pressure, the bypass valve 101a is
opened further until in the fully opened position. At this point,
or else at a pre-set opening point, the throttle valve 102 begins
to close thus maintain the required intermediate pressure steam
turbine 34 exit pressure at level required to supply steam to the
lignite dryer 10. The operation limit of the additional extraction
with this arrangement, without use of the first extraction may be
limited by the maximum low pressure steam turbine 35 steam
temperature limit. As a result, this solution is most applicable
for high loads, for example above 70%, as low pressure steam
turbine 35 temperature limitations typically limit throttling at
lower load.
[0032] In an exemplary embodiment where temperature limitations of
the low pressure steam turbine 35 are reached, the bypass valve
101a is closed while steam in the additional extraction line 101 is
mixed with hot reheat extraction steam from the first extraction
104 using the ejector 106. This arrangement may be used for middle
and low water/steam power cycle loads down, for example, 35% or
even lower, depending on the design limits of the water/steam power
cycle components. The control of the exemplary embodiment may be
further enhance by providing a first control valve 104a in the
first extraction line 104 upstream of the ejector 106 and a second
control valve 101b in the second extraction line 101 upstream of
the ejector 106. In this arrangement the flow-rate to the heater is
further controlled in further conjunction with the first control
valve 104a and the second control valve 101b.
[0033] Although the disclosure has been herein shown and described
in what is conceived to be the most practical exemplary embodiment,
the present disclosure can be embodied in other specific forms. The
presently disclosed embodiments are therefore considered in all
respects to be illustrative and not restricted. The scope of the
disclosure is indicated by the appended claims rather that the
foregoing description and all changes that come within the meaning
and range and equivalences thereof are intended to be embraced
therein.
* * * * *